If $a + b = 2$ and $x + y + z = -10$, what is $-y - x + 6a + 6b - z$ ?
Solution: $= 6a + 6b - x - y - z$ $= (6) \cdot (a + b) + (-1) \cdot (x + y + z)$ $= (6) \cdot (2) + (-1) \cdot (-10)$ $= 12 + 10$ $= 22$